Row-column repair technique for semiconductor memory arrays

Abstract

A method for locating a repair solution for a memory that includes a memory array containing a plurality of rows and a plurality of columns, N redundant rows, and M redundant columns. Both N and M are integers, where N is greater than or equal to zero and M is greater than or equal to zero. The N redundant rows and the M redundant columns are collectively referred to as redundant lines. The method includes generating a first defect matrix defects in the memory array. Additionally, the method includes recursively, until either the repair solution is found or the redundant lines are consumed: selecting a first line in the defect matrix and having at least one defect; generating a second defect matrix by eliminating at least the defects in the first line from the first defect matrix; and determining if the repair solution is found.

What is claimed is:  
     
       1. A method for locating a repair solution for a memory that includes a memory array comprising a plurality of rows and a plurality of columns, N redundant rows, and M redundant columns, where N and M are integers and where N is greater than or equal to zero and M is greater than or equal to zero, and wherein the N redundant rows and the M redundant columns are collectively redundant lines, the method comprising: 
       generating a first defect matrix representing defects in the memory array;  
       recursively, until either the repair solution is found or the redundant lines are consumed:  
       selecting a first line represented in the defect matrix and having at least one defect;  
       generating a second defect matrix by eliminating at least the defects in the first line from the first defect matrix; and  
       determine if the repair solution is found.  
     
     
       2. The method as recited in  claim 1  further comprising: 
       selecting a first repair option for the first line as either (i) one of the redundant lines, or (ii) one or more redundant cross lines; wherein, if the first line is a row then the redundant columns are redundant cross lines, and wherein, if the first line is a column then the redundant rows are redundant cross lines.  
     
     
       3. The method as recited in  claim 2  wherein, if the first repair option does not result in a solution, the method further comprises: 
       selecting a second repair option as the one of (i) and (ii) that was not selected as the first repair option; and  
       recursively, until either the repair solution is found or the redundant lines are consumed: selecting the first line, generating the second defect matrix; and determining if the solution is found.  
     
     
       4. The method as recited in  claim 3  wherein, if no repair solution is found with the second repair option, then there is no repair solution for the memory. 
     
     
       5. The method as recited in  claim 1  further comprising filtering out must-replace rows prior to beginning recursion. 
     
     
       6. The method as recited in  claim 5  further comprising, prior to selecting the first line, filtering out must-replace rows and must-replace columns. 
     
     
       7. The method as recited in  claim 6  wherein, if a result of filtering out the must-replace rows and must-replace columns is that there are zero remaining redundant rows or zero remaining redundant columns, then a repair solution is located for the memory. 
     
     
       8. The method as recited in  claim 5  wherein, if a number of remaining redundant rows after the filtering is less than zero, then there is no repair solution for the memory. 
     
     
       9. The method as recited in  claim 5  further comprising checking an upper bound of a number of repairable defects against a number of defects represented in the defect matrix, and determining that there is no solution if the number of defects exceeds the number of repairable defects. 
     
     
       10. The method as recited in  claim 9  wherein an upper bound for a number of columns having defects is the sum of a number of available redundant columns and the product of the number of available redundant columns and the number of available redundant rows. 
     
     
       11. The method as recited in  claim 9  wherein an upper bound for a number of rows having defects is the sum of a number of available redundant rows and the product of a number of available redundant columns and a number of available redundant rows. 
     
     
       12. A computer accessible medium comprising one or more instructions which, when executed, perform a method for locating a repair solution for a memory that includes a memory array comprising a plurality of rows and a plurality of columns, N redundant rows, and M redundant columns, where N and M are integers and where N is greater than or equal to zero and M is greater than or equal to zero, and wherein the N redundant rows and the M redundant columns are collectively redundant lines, the method comprising: 
       generating a first defect matrix representing defects in the memory array;  
       recursively, until either the repair solution is found or the redundant lines are consumed:  
       selecting a first line represented in the defect matrix and having at least one defect;  
       generating a second defect matrix by eliminating at least the defects in the first line from the first defect matrix; and  
       determining if the repair solution is found.  
     
     
       13. The computer accessible medium as recited in  claim 12  wherein the method further comprises: 
       selecting a first repair option for the first line as either (i) one of the redundant lines, or (ii) one or more redundant cross lines; wherein, if the first line is a row then the redundant columns are redundant cross lines, and wherein, if the first line is a column then the redundant rows are redundant cross lines.  
     
     
       14. The computer accessible medium as recited in  claim 13  wherein, if the first repair option does not result in a solution, the method further comprises: 
       selecting a second repair option as the one of (i) and (ii) that was not selected as the first repair option; and  
       recursively, until either the repair solution is found or the redundant lines are consumed: selecting the first line, generating the second defect matrix; and determining if the solution is found.  
     
     
       15. The computer accessible medium as recited in  claim 14  wherein, if no repair solution is found with the second repair option, then there is no repair solution for the memory. 
     
     
       16. The computer accessible medium as recited in  claim 12  wherein the method further comprises filtering out must-replace rows prior to beginning recursion. 
     
     
       17. The computer accessible medium as recited in  claim 16  wherein the method further comprises, prior to selecting the first line, filtering out must-replace rows and must-replace columns. 
     
     
       18. The computer accessible medium as recited in  claim 17  wherein, if a result of filtering out the must-replace rows and must-replace columns is that there are zero remaining redundant rows or zero remaining redundant columns, then a repair solution is located for the memory. 
     
     
       19. The computer accessible medium as recited in  claim 16  wherein, if a number of remaining redundant rows after the filtering is less than zero, then there is no repair solution for the memory. 
     
     
       20. The computer accessible medium as recited in  claim 16  wherein the method further comprises checking an upper bound of a number of repairable defects against a number of defects represented in the defect matrix, and determining that there is no solution if the number of defects exceeds the number of repairable defects. 
     
     
       21. The computer accessible medium as recited in  claim 20  wherein an upper bound for a number of columns having defects is the sum of a number of available redundant columns and the product of the number of available redundant columns and the number of available redundant rows. 
     
     
       22. The computer accessible medium as recited in  claim 20  wherein an upper bound for a number of rows having defects is the sum of a number of available redundant rows and the product of a number of available redundant columns and a number of available redundant rows. 
     
     
       23. An integrated circuit comprising: 
       a memory that includes a memory array comprising a plurality of rows and a plurality of columns, N redundant rows, and M redundant columns, where N and M are integers and where N is greater than or equal to zero and M is greater than or equal to zero; and  
       a circuit coupled to the memory, the circuit configured to:  
       generate a first defect matrix representing defects in the memory array;  
       recursively, until either the repair solution is found or the redundant lines are consumed:  
       select a first line represented in the defect matrix and having at least one defect;  
       generate a second defect matrix by eliminating at least the defects in the first line from the first defect matrix; and  
       determine if the repair solution is found.